AI writing tools in 2026 mostly follow a free-tier-plus-subscription model, and the free tier usually stops at the point where you need unlimited rewriting, long documents, or team features — not at the point where you first type a sentence.
According to our AI tool database, Grammarly offers a free basic tier and a Pro plan at $12 per month, QuillBot has a free tier and a Premium plan at $4.17 per month billed annually, and ProWritingAid runs a free tier alongside Premium at $30 per month or $360 per year, Premium Pro at $12 per month or $144 per year, and one-time lifetime licenses at $399 and $699.
Those are the recorded prices at verification time, and they show how wide the spread is: two tools that do broadly similar work can sit four times apart on monthly cost.
The mechanism behind that spread is what each tool counts as a "use." Free tiers are not usually crippled by hiding features — they are capped by volume. A grammar checker can afford to give away unlimited basic corrections because the free version is also a funnel for its paid upgrade.
A paraphrasing tool cannot, because every rewrite costs the company real computing power, so the free tier limits how many words you can process at once or how many rewrites you get per day. ProWritingAid's structure is the clearest illustration of this: the same underlying engine is sold as a monthly subscription, an annual subscription, or a lifetime license, which tells you the company is pricing access duration rather than access depth.
When you compare tools, ask what unit gets metered — words, documents, rewrites, or seats — because that is the number that will actually interrupt your work.
A concrete example makes this real. Say you write three 1,200-word blog posts a week and want each one checked for style and rewritten in two or three different tones. On Grammarly's free tier you get basic checking but not the context-aware style adjustment that Pro offers, so you would be upgrading to the $12 per month plan.
On QuillBot's free tier you would hit rewrite limits quickly at that volume, pushing you toward Premium at $4.17 per month billed annually. On ProWritingAid's free tier the long-document reports are the thing you would miss, and your cheapest paid route is Premium Pro at $12 per month or $144 per year.
Notice that the "cheapest" answer changes depending on which feature you actually need — the $4.17 plan is not cheaper than the $12 plan if it does not do the job you have.
Here is where this advice breaks down. Prices in this category move often, and the figures above are a snapshot recorded at verification time, not a promise. Vendors change plan names, move features between tiers, and quietly raise renewal prices; the only reliable source for what you will pay today is the vendor's own pricing page.
Annual billing looks cheaper per month but locks you in, so if you are unsure whether a tool fits your workflow, start monthly. Lifetime licenses sound like a bargain, but they only pay off if the tool still exists and still gets updates in five years — that is a real risk in a market this crowded.
And none of these tools replace editing judgment. A $12 per month subscription that produces text you still rewrite by hand is more expensive than a free tier you use carefully.
One tip that saves more money than any plan comparison: audit your actual usage for two weeks before you upgrade. Most people overestimate how often they hit free-tier limits and underestimate how much of their writing is short enough for a free plan. If you are weighing whether a paid AI subscription is worth it at all, our breakdown of How much does ChatGPT Plus cost in 2026, and is it worth paying for? walks through the same trade-off for a general-purpose assistant rather than a writing specialist.